What is Roof Flashing?
Roof flashing is basically a thin material – typically a galvanized steel – that professional roofers will use in order to direct water away from the critical areas of the roof. Typically, it is wherever the roof plan meets a vertical surface like a dormer or a wall.
The Basics of Roof Flashing Installation
The flashing is installed to surround the features of the roof, like chimneys, vents, and skylights. Water should then run down the side of the flashing and wind up getting directed to the shingles instead of finding a way into the roof deck.
The Purpose of Roof Flashing
Without the roof flashing against those walls, water would slowly drip into the space between the roof and wall, and even potentially into the home. So, what do you do when you find yourself needing roof flashing? Knowing the different types as well as the techniques to implement can be helpful.
Roof Flashing Types
- Continuous Flashing. This is also known as “apron flashing” because it acts in a similar manner to an apron. It is a long, single piece of metal that is used to carry the water down to the shingles that lay below.
- Base Flashing. There are some roof features, like chimneys, that require two pieces of flashing. This is to ensure that the rain always meets a flashing surface to direct it downward. Not only that, it is notoriously difficult to install flashing around a chimney.
- Counter Flashing. This is placed opposite of base flashing, or above base flashing. Counter flashing completes the team with the aforementioned base flashing.
- Step Flashing. This is a rectangular piece of flashing that is bent 90 degrees in the middle. It is generally used for wall flashing. In this instance, multiple pieces of flashing will be installed as layers with the shingles to make sure that the water flows away from the wall.
- Skylight Flashing. There are some skylight manufacturers that include flashing with their product, but others will require you to create it or purchase it separately. Knowing which option you have beforehand is helpful.
- Valley Flashing. Any open valleys on your roof have metal flashing in order to protect this area, which is a critical area of the roof.
- Drip Edges. At the edge of the roof, there is a thin metal flashing that allows water to drip off the roof without doing damage to the home or causing a pesky leak that can do further damage to the roof or home.
- Kickout Flashing. Roofing contractors generally need something to bridge the gap where the step flashing comes to an end and where the gutter begins. This kind of flashing is used to direct water away from the wall and down into the gutter.
There are also a few different roofing materials that you need to be aware of. In the past, this would be lead or materials that were lead-coated. Now, professionals throughout North America have switched to one of three materials.
Roof Flashing Materials
- Aluminum flashing is generally easy for roofers to form and it is also quite lightweight. There is one thing to note, however: aluminum has to be coated if it is going to be used with masonry and concrete since plain aluminum degrades and reacts when it makes contact with alkaline surfaces.
- Copper roof flashing takes soldering well and is also malleable. Not only that, it is highly durable and tends to have a longer-lasting life. On the other hand, there is some discoloring into patina, which can vary based on the homeowner. Copper flashing is routinely found around chimneys.
- Steel flashing is the most popular choice for flashing. In addition to aesthetic value, it is also malleable and, when galvanized, is corrosion-resistant.
There are building codes to be aware of that may call out a specific material. Have your roofing contractor look into this so that you can be covered in the event that a certain material is disallowed.
Identifying Roof Flashing Types
There are quite a few types of roof flashing; nearly as many as there are parts to the roof. Each roof feature requires protection, hence why there are so many different types of roof flashing.
Longer pieces of continuous flashing have trouble flexing as the home contracts and expand during the changing of the seasons. If left alone, it could warp or break and fail to keep that water out. If using longer pieces, they should have built-in expansion joints so that they can move as the home does.
Another benefit to two-part flashing is that when the roofing materials expand and contract with the weather, those two pieces can move, so the system stays secure.
So, how do you properly install roof flashing? Here are a few helpful techniques.
Roof Flashing Techniques
- Step Flashing. The best instance for step flashing is where the roof face meets a wall. An example of this is where the dormer projects out from the roof. In a spot like this, it is entirely possible that water could flow down the wall and get past the shingles into the building down below.
- Plumbing vent boot flashing. To put it simply vent flashing is the kind of flashing that has a cylindrical piece of flashing. This piece of flashing fits around the vent itself. These shingles are installed over the base or the boot. The height of the boot is meant to force water to run around the vent itself.
- Counter Flashing. Counter-flashing is most commonly used to flash chimneys and involves two pieces of flashing. The first piece, the base flashing, is meant to sit around the base of the chimney. The second piece, the counter-flashing itself, finds itself embedded into the masonry of the chimney. This piece sits over the base flashing. It is meant to ensure that the water doesn’t slip in behind the base flashing. Professional contractors generally use counter-flashing for a litany of other purposes, but it typically involves a second piece of flashing that is set off from the first.
Before you can learn to install that roof flashing, you need to understand the three primary techniques that are involved. Each one is different and can be suitable for different areas of the roof. There are also flashing types that tend to correspond with a specific technique.
Step flashing is the way to ensure that the water is properly directed away from the wall and that it winds up in the gutter. This is called step flashing because it is installed in – you guessed it – steps. This involves layers of shingles between so that the water gets poured down each step and then down the roof.
The main key when installing roof flashing is to use a sealant. There are roofing professionals out there, generally of the old school variety, that still use nails while flashing. This works, but they still need to choose whether to nail to the roof plane or to the vertical wall itself.
If the contractor decides to nail to both, the flashing could deform under the pressure from shifting wood or brick. If you decide to use nails and nail only to the roof plane or to the vertical wall, the flashing can then stay in place while the other materials used in the construction contract and expand as the weather changes.
It is that weather change that can cause the most havoc. If the wrong materials are used or they are installed in an improper manner, that constant expansion and contraction can lead to the materials to bend and warp, making it more brittle until it finally breaks.
That is why roofing cement is generally accepted as the most common type of roofing sealant. This is because roofing cement is meant to create a waterproof seal. Roofing professionals can use a trowel to apply it evenly so that it adheres properly.
Protecting Your Roof
Ultimately, the installation of flashing and the application of a proper sealant are meant to protect your roof and its trouble areas from water and other damaging elements. Those hard to reach areas can be the first to go without proper flashing, so it is imperative for the life of your roof that you have to flash that will expand and contract with the elements and divert the water off the roof.
Those tough to reach areas can go unnoticed by amateur roofers who may not have the knowledge or experience necessary. Having a proper roofing contractor is necessary to ensure that those trouble areas do not worsen.
If not handled properly, areas around vents or the chimney could have a pooling of water. This water can do damage to areas of the roof, creating discoloration and even leaks. Those leaks can be a real trouble area if left unchecked, potentially causing structural damage if left unchecked.
A proper roof flashing can do wonders for protecting your roof from water damage and unnecessary wear and tear to those trouble areas on your roof.